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OBD-II Code

P0977

Severity

Not yet reviewed

Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.

Can you drive it

We cannot say

Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.

Indicative cost (USD)

$300–$1,500

From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.

P0977 is the Shift Solenoid B Control Circuit High — the TCM commands SS-B and reads voltage stuck high (open circuit, no current flowing when current was expected).

How a shop works this

Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.

  1. Note every code that is set, not just this one.

    Codes that appear together usually narrow the cause faster than any one of them read alone.

  2. Read the freeze frame — the conditions the fault was recorded under.

    Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.

  3. Confirm the fault is current rather than history.

    Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.

  4. Then follow the diagnostic notes further down this page, in the order they are written.

    They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.

If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.

Common symptoms

  • Check engine light
Read the full diagnostic procedureP0977 is the Shift Solenoid B Control Circuit High — the TCM commands SS-B and reads voltage stuck high (open circuit, no current flowing when curren…

P0977 is the Shift Solenoid B Control Circuit High — the TCM commands SS-B and reads voltage stuck high (open circuit, no current flowing when current was expected). The cause is an open wire, an open solenoid winding, a pushed-back pin at the case connector, or a TCM driver gone open-circuit.

Cheapest-first

  1. pull the case connector and inspect for pushed-back terminals or green-fuzz corrosion from ATF wicking up the pins — this is the #1 cause and costs zero to find.
  2. Ohm SS-B at the case connector pin-to-pin: 8-30 ohms is the typical spec (19-31 ohms GM 4L60E, 9-16 ohms Ford 4R75W, 11-15 ohms Chrysler 545RFE pack, 10-15 ohms Toyota A340/A750).
  3. Infinite ohms = open winding, solenoid (or pack) replacement.
  4. In-spec ohms at the case = the open is upstream, back-probe the harness between TCM and case connector and ohm each conductor end-to-end (wire resistance should be under 5 ohms on a short run; anything higher means a corroded splice, pushed pin, or break).
  5. Ohms-to-ground on each pin should be >100k ohms (floating).
  6. Active current at full command should be 0.5-1.5 A — read zero current with the driver commanded on and the open is confirmed.
  7. Expensive-misdiagnosis caveat: on Chrysler 545RFE/68RFE intermittent or stable P0977 is frequently the result of an internal pack solder-joint failure that thermally cycles open — passes cold, opens hot, returns at temp — and only full solenoid-pack replacement clears it.
  8. RAM trans techs at AAMCO and independent shops aggregate this as one of the highest-frequency 545RFE/68RFE codes in the 70k-150k mile band, and chasing individual wires on this trans is a known waste of customer money.
Vehicle-specific patterns1996-2007 GM 4L60E/4L65E throws P0977 from case-connector pin-fit loss after repeated unplugging during routine fluid service — GM service guidance i…
  • 1996-2007GM 4L60E/4L65E throws P0977 from case-connector pin-fit loss after repeated unplugging during routine fluid service — GM service guidance is to replace the case-connector body rather than just spraying contact cleaner, $40-80 part.
  • 2003-2010Dodge Ram 1500/2500 with the 545RFE and 2007-up 68RFE sets P0977 as a near-certain pack-failure indicator in the 70,000-150,000 mile band — pack replacement $500-900 parts plus labor at independents per AAMCO/RepairPal aggregated cost data.
  • 2007-2013Ram HD with the Aisin AS69RC throws P0977 from a documented internal pigtail solder-joint break inside the valve-body solenoid carrier, valve-body R&R required, $800-1,400.
  • 2001-2010GM HD with the Allison 1000 (LCT1000) sets the equivalent open-circuit from PCS-2/PCS-3 wire-break at the case-flange ridge chafe location — repair the wire before condemning the solenoid, per Allison service guidance.

Estimated repair$300 to $1,500.

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